Sheet Music Collection Ringbinder

[son of frog]

So i have a huge collection of transcriptions, sheet music and tab etc. all on hundreds of sheets,

And i have a Leather Zip up Ring-binder, and of course am using clear plastic sleeves to keep it all organized in there,
Although at this rate i may be expanding to another ring-binder,

But i was wondering, does anyone know a good, and preferably reasonably priced store, be it online or on the high street where i can get these plastic sleeves, but semi or fully Rigid? but still with the 4 holes to attach to a standard A4 ring-binder?

Also they need to be clear to view said sheet music on both sides,
The main problem is i cant tell which ones being sold online are rigid and which arent, a lot of manufacturers / stores are very vague, and it would be miles easier to find someone on here with something similar, than to try and email each individual company asking 20 questions about the size / thickness of their binder sleeves.

Thanks in advance for any help,
I've never failed to get a helpful answer yet on this Forum.

-Tom